Behavioral Assays

This system automtically screens olfactory responses of 15 individual flies to up to 8 odors and all potential mixtures of those odors. In short, the flies are placed in 15 aligned glass tubes and under red light XY positions of the flies are monitored continuously by an overhead camera.

The flies are continuously exposed to a humidified airflow and are repeatedly presented with pulses of various olfactory stimuli at interstimulus intervals of 90 s. Attractive odors provoke upwind movement of the flies, while repellent odors provoke no or downwind movement.

As flies are allowed to distribute freely within their glass tubes, they may encounter the odor pulse at different times. This is compensated for by calculating the time of odor encounter for each individual tracking event based on the X position of the fly, system intrinsic delay, and airspeed.

Flywalk does not only allow to screen the valence of many odors in many flies, but also provides detailed information about response latency (the most attractive odorants result in upwind movement already 200 ms after stimulus arrival) and response strength. For details see

This assay provides a quick and easy method to test the valence of individual odorants in Drosophila. An odor-containing and a solvent containing trap made from 30-mL transparent plastic vials are placed into a 500-ml box with ventilation holes in the lids. Thirty 4- to 5-d-old starved flies are placed in each test box. Experiments are carried out in a climate chamber (25 °C, 70% humidity, 12:12 light:dark cycle). The number of flies inside and outside the traps is counted after 24 h. The attraction index oft he odorant is calculated as (O − C)/T, where O is the number of flies in the odorant trap, C is the number of flies in the control trap, and T is the total number of tested flies. For example studies using the trap assay see

Knaden et al. Cell reports. 2012

Keesey et al. Chemical ecology. 2016